When a panel of Belgian jurors convicted four Rwandans of participating in the 1994 genocide in their country, they pioneered a new brand of "universal justice" that knows no borders.

The verdict, handed down early Friday morning after 11 hours of deliberation in the gloomy granite Palace of Justice in Brussels, marked the first time that a civilian jury - not a judge - in one country had judged crimes against humanity committed elsewhere.

"Every citizen of the world is concerned by a crime against humanity," said Michele Hirsch, a lawyer for relatives of victims of the genocide, in which as many as 800,000 ethnic Tutsis and moderate Hutus were killed. "That makes every citizen competent to sit in judgment of such crimes."

"I hope that this is going to push the idea of universal justice, that it will be a springboard for other such cases," said Reed Brody, advocacy director of Human Rights Watch in New York.

The jury found the defendants, including two Roman Catholic nuns, guilty on most of the 55 counts against them, including murder and incitement to genocide. Witnesses called during the seven-week trial testified that the nuns had encouraged and collaborated with Hutu extremists who butchered and burned several thousand Tutsi refugees who had sought shelter in their convent. The nuns, a former government minister, and a former university professor were sentenced to between 12 and 20 years in prison.

The case was brought by Rwandan Tutsi exiles in Belgium, who had recognized on the streets of Brussels some of the Hutu extremists who carried out the genocide. They made use of a 1993 Belgian law that allows courts here to try cases of atrocities regardless of where they were committed. The defendant does not even have to be in Belgium to stand trial.

That law proved an embarrassment to the Belgian government last week, when it emerged that a private group had filed charges with judicial authorities here against Israeli Prime Minister Ariel Sharon, for his role in the massacre of Palestinians by Christian militia in the Sabra and Shatila refugee camps in Lebanon in 1982, when Mr. Sharon was defense minister.

The law does not offer immunity to serving heads of state or government, or to other officials accused of genocide, war crimes, or other crimes against humanity.

Belgian Foreign Minister Louis Michel said on Wednesday his government would "try to correct" aspects of the law. Diplomats said the law as it stands could hobble Belgian international relations. Brussels could not hope to mediate the Middle East conflict, for example, if Belgian courts were investigating the Israeli prime minister's alleged involvement in war crimes.

Mr. Michel added, however, that he remained committed to the principle behind the law, giving Belgian courts the right to try foreigners for foreign atrocities.

In fact, countries that ratify the 1949 Geneva Convention are bound to try such cases, but few actually do so. "We are unusual and ordinary at the same time," says Gerard Dive, the Belgian Justice Ministry's head of international criminal law. "We simply do in practice what everybody should be doing, but there is a habit of shutting ones' eyes."

A Belgian magistrate is currently investigating former Chadian dictator Hissene Habre, under whose 1982-90 rule some 40,000 political killings are said to have occurred. Private citizens have filed a complaint against former Iranian President Hashemi Rafsanjani for alleged torture of political prisoners.

A number of other countries have begun to take similar action to apply "universal justice." Most famously, Britain detained former Chilean dictator Augusto Pinochet for more than a year while the courts heard an extradition case against him filed by a Spanish judge who was investigating the disappearance of Spanish citizens in Chile during General Pinochet's rule.

Courts in Germany, Holland, and Denmark are prosecuting or have sentenced Bosnian Serbs and Muslims to jail for crimes during the Balkan wars; Mexico has agreed to extradite to Spain an alleged Argentinian torturer; and France began to prosecute an alleged torturer from Mali before he slipped out of the country last year.

Other countries have preferred not to prosecute such cases: Austria let a top aide to Iraq's Saddam Hussein leave Vienna in 1999 even though a criminal complaint had been filed against him with a local court. South African police did not arrest former Ethiopian tyrant Mengistu Haile Mariam when he visited South Africa two years ago, even though he is wanted in his home country for crimes against humanity. And in the United States, when the Justice Department detained an alleged Peruvian torturer last year, the State Department intervened to ensure his safe return home.

"Belgium is setting an example, and I hope it is a precedent other countries will follow," says Alain Destexhe, a Belgian senator who led a parliamentary inquiry into the genocide in Rwanda, a former Belgian colony. "It makes sense only if other countries follow suit" to ensure there is no haven for war criminals.

Though some observers had wondered whether a jury of 12 ordinary Belgians - they included a hairdresser, a truck driver, a university teacher, and a journalist - would be able to understand enough about the extraordinary, unfamiliar, and horrific events they were judging to reach an informed verdict, the result appeared to quell such doubts.

They picked their way carefully through the accusations, confirming some and rejecting others by votes that often split the jury 7 to 5.

The trial, says Mr. Brody, "showed it can be done. You can ask citizens to determine right and wrong in a lot of different circumstances. This is a major step forward for the principle that justice has no borders."